1. Field of the Invention
The present invention relates to a rotation sensor-equipped bearing and particularly it relates to an outer ring rotation stop construction.
2. Brief Description of the Prior Art
Detection of rotational speed (rpm) of a bearing has heretofore been made by installing a rotation sensor in close vicinity to the bearing. Recently, however, for the sake of facilitation of installation and effective use of space, rotation sensor-equipped bearings with a rotation sensor fixed to the bearing have been proposed.
A conventional example of such rotation sensor-equipped bearing will be described with reference to the drawings. FIG. 2(A) is a front view of the rotation sensor section, which is the principal portion of a rotation sensor-equipped bearing, and FIG. 2(B) is a sectional view thereof.
In FIG. 2, the numeral 21 denotes a bearing comprising an inner ring 22, an outer ring 23, a plurality of rolling elements 24 rollably disposed between the inner and outer rings 22 and 23, and a cage 25 for rollably receiving said rolling elements 24 at a predetermined pitch. The outer diameter portion of said outer ring 23 is mounted to the inner diameter portion of a bearing housing 26. The numeral 27 denotes rotation sensor comprising an encoder 28, such as a magnetic encoder, fixed to said inner ring 22, a core metal 29 mounted to said outer ring 23, a sensor housing 30 fixed to said core metal 29, a sensor 31 fixed within the sensor housing 30, a circuit board 32 having a circuit incorporated therein for processing electric signals obtained by the sensor 31, an electric wire 33 for taking the detected rotational speed (rpm) from the circuit board 32, wherein the sensor 31, circuit board 32, the connected end of electric wire 33, etc., within said sensor housing 30 are molded with resin. Further, a hold-down lid 34 is attached to a bearing housing 26 by fixing members 35 such as machine screws at a plurality of circumferential places. The electric wire 33 is taken out to the outside through a notch groove 34a formed in the hold-down lid 34.
And, when the inner ring 22 rotates, the encoder 28 mounted to this inner ring 22 rotates with the inner ring 22 and concomitantly therewith its position relative to the sensor 31 periodically changes, whereby the sensor 31 detects the rotational speed (rpm) of the inner ring 22, the detected rotational speed (rpm) being taken out as an electric signal to the outside by the electric wire 33.
However, in the conventional rotation sensor-equipped bearing described above, since the outer ring 23 is mounted by fitting in the bearing housing 26, the difference in thermal expansion between the outer ring 23 and the bearing housing 26, and other factors cause the clearance between the outer diameter of the outer ring 23 and the inner diameter of the bearing housing 26 to exceed the allowable limit, so that with the rotation of the inner ring 22, the outer ring 23 sometimes rotates along the direction of rotation of the inner ring 22. If the outer ring 23 should rotate, the sensor housing 30 mounted to the outer ring 23 will simultaneously rotate, resulting in a shearing force being applied to the electric wire 33 taken out of the sensor housing 30 since the latter is taken out to the outside through the notch groove 34a formed in the hold-down lid 34 fixed to the bearing housing 26. Therefore, in extreme cases, the electric wire 33 sometimes breaks.
Accordingly, it is an object of the invention to provide a rotation sensor-equipped bearing, such as the one described above, having a rotation stop construction for the outer ring capable of preventing the rotation of the outer ring and the breakage of the electric wire when the outer ring tends to rotate.
A rotation sensor-equipped bearing described in claim 1, for solving said problem, comprises an inner ring, an outer ring, a plurality of rolling elements received between said inner and outer rings, said inner ring constituting a rotatable raceway ring, an encoder mounted to one end of said rotatable raceway ring, said outer ring being mounted to the bearing housing to constitute a fixed raceway ring, a sensor mounted to said fixed raceway ring in a position opposed to said encoder through a core metal, and a hold-down lid fixed to said bearing housing, said rotation sensor-equipped bearing being characterized in that the outer diameter surface of a sensor housing receiving said sensor is provided with a rotation stop member radially projecting through said core metal, said rotation stop member being disposed in a notch groove in said hold-down lid.
Thus, providing the outer diameter surface of the sensor housing receiving the sensor with the rotation stop member radially projecting through said core metal and disposing the rotation stop member in the notch groove in said hold-down lid ensures that even if a turning force is produced in the bearing outer ring, the disposition of the rotation stop member in the notch groove in the hold-down lid results in the rotation stop member abutting against the inner wall surface of the notch groove in the hold-down lid, thereby reliably preventing the rotation of the bearing outer ring. Simultaneously, since the rotation stop member serves as a fixing member for the electric wire, the pull-out strength of the electric wire is improved, thus preventing the breakage of the electric wire.
A rotation sensor-equipped bearing of the invention is characterized in that the rotation stop member is integral with the sensor housing.
Thus, this construction in which the rotation stop member is integral with the sensor housing eliminates the possibility of the rotation stop member rotating relative to the sensor housing and makes it possible to omit the operation of attaching the rotation stop member to the sensor housing.
A rotation sensor-equipped bearing of the invention is characterized in that the rotation stop member is separate from the sensor housing member and is attached to said sensor housing member.
Thus, this construction in which the rotation stop member is separate from the sensor housing member and is attached to said sensor housing member allows separate fabrication of the rotation stop member and sensor housing, so that as compared with the case of constructing the rotation stop member to be integral with the sensor housing member, fabrication molds are simplified and so is the production, and moreover, even if the rotation stop member or the sensor housing member should be partly damaged and discarded, discarding the whole of the rotation stop member and sensor housing member is saved.